Practicum is an excellent chance for university students to apply their knowledge in a real-world professional setting. Unlike other majors, Vietnamese English major students are generally not trained to work in a particular area. Therefore, the causes of their unsatisfactory experiences during practicum are different from those of students with other majors. This current study was designed with a mixed-methods approach to enlist the causes of English-majored students’ unsatisfactory experiences during their practicum. Two hundred twenty-two interns majoring in English studies/linguistics responded to an open-ended question. The results showed that students’ low self-efficacy and short internship duration were the two leading causes of unsatisfactory experiences during the practicum. Based on the qualitative data analyses, the students were found struggling to complete their assigned tasks as well as expected. Additionally, the short duration prevented them from gaining more professional experience. As a result, some implications for improving the program’s quality are discussed in this paper.